Lipids (fats and oils) constitute between 30 and 40% of the caloric intake of the average American diet. Dietary fat, consisting of triglycerides, is digested to free fatty acids and monoglycerides, primarily in the small intestine. The .alpha.-lipase steapsin cleaves the glycerol esters at the 1- and 3- positions. Fatty acids of 6 to 10 carbons and unsaturated fatty acids are rapidly absorbed, while those of 12 to 18 carbons are absorbed more slowly. Absorption of the .beta.-monoglycerides by the mucosa of the small intestine results in a final digestion and absorption of up to 95% of the total dietary fat. Since fats yield about twice the energy per gram of either carbohydrates or proteins, substitution of a non-digestible material for a portion of the normal dietary fat offers a painless and effective method for control of obesity, hypertension, and other diseases associated with excessive caloric intake.
There is considerable evidence that steapsin is an enzyme which is specific for esters of 1, 3-diols and glycerol. U.S. Pat. No. 2,962,419 to Minich describes in vitro tests of pentaerythretol tetracaprylate to demonstrate that there is no hydrolysis of the pentaerythritol ester by pancreatic lipase (steapsin) and a greatly diminished total serum lipid concentration when the substance was used in place of fat in a typical rat diet. Canadian Pat. No. 1,106,681 to Trost describes the feeding of dialkyl glycerol ethers to rats, concluding that the esters were generally non-digestible, and tests of sucrose polyester in obese human volunteers showed decreased total plasma cholesterol and plasma triglycerides (Glueck et al., Am. J. Cli. Nutri., 35, 1352 (1982)). U.S. Pat. No. 3,600,186 to Mattson et al. describe the use of fatty acid ester compounds having at least 4 fatty acid ester groups for use as triglyceride fat substitutes.
Esters of malonic acid and dialkyl malonic acid, and low molecular weight alcohols are known but are unsuitable for use as vegetable oil substitutes due to their low boiling points.
There remains a need for stable synthetic oils which are not readily digestible in mammals, and which are suitable for use in the production of low calorie fried and baked products containing starches, and in other foods such as oleomargarine, salad oil and other foods normally containing vegetable oils.